Devices including laptop or desktop computers, tablet computers, televisions, digital video recorders, set-top boxes, digital media players, video gaming devices, video game consoles, and cellular telephones may include one or more graphics processing units (GPUs). A GPU may include multiple cores. GPUs may utilize one or more wired communication protocols for communications. To conserve power, a GPU may cause one or more of the cores to enter a low power state.
The I2C-bus (Inter-IC) specification defines a two-wire bidirectional bus for efficient inter-IC (integrated circuit) control. The System Management Bus (SMBus) specification is based on I2C and defines another protocol for the two-wire bidirectional bus interface. For both the I2C-bus and SMBus, a serial data line and a serial clock line are used to transfer data from one device connected to the bus to another device connected to the bus. In both I2C-bus and SMBus a device that initiates a data transfer is referred to as a master device and a device that is addressed by a master is referred to as a slave device. A data transfer may be dropped if a slave device is in a low power state when a master initiates a data transfer.